A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions

A61C7/002—Orthodontic computer assisted systems

Abstract

Systems and methods are disclosed for performing virtual treatment using one or more dental appliances by receiving a digital model of a dental appliance; selecting a standard position and orientation; and mapping the digital model of the dental appliance to the standard position and orientation.

Description

SYSTEMS AND METHODS FOR SUBSTITUTING VIRTUAL DENTAL

APPLIANCES ' INVENTOR: PETER G. KNOPP

BACKGROUND

[0001] The invention relates generally to computer-automated development of an orthodontic treatment and appliance.

[0002] Orthodontics is the branch of dentistry that deals with the straightening of crooked teeth. Although there are many types of appliances that can be used by an orthodontist to straighten the teeth, the most common appliance is braces. Braces include a variety of appliances such as brackets, archwires, ligatures, and O-rings, and attaching braces to a patient's teeth is a tedious and time consuming enterprise requiring many meetings with the treating orthodontist. Consequently, conventional orthodontic treatment limits an orthodontist's patient capacity and makes orthodontic treatment quite expensive.

[0003] Before fastening braces to a patient's teeth, at least one appointment is typically scheduled with the orthodontist, dentist, and/or X-ray laboratory so that X-rays and photographs of the patient's teeth and jaw structure can be taken. Also during this preliminary meeting, or possibly at a later meeting, an alginate mold of the patient's teeth is typically made. This mold provides a model of the patient's teeth that the orthodontist < uses in conjunction with the X-rays and photographs to formulate a treatment strategy. The orthodontist then typically schedules one or more appointments during which braces will be attached to the patient's teeth.
[0004] Historically, the practice of orthodontics has been a manual process that relied on the doctor's skills and judgment. A number of parties are creating and providing products and services that can be grouped together under the appellation 'virtual orthodontics'. The principle elements of virtual orthodontics are representations of the teeth and of orthodontic components such as brackets and wire. [0005] One of the values of virtual orthodontics is that the user can make choices among available components before actually implementing the treatment approach. For instance, an orthodontist can evaluate options by choosing different bracket prescriptions and features such as hooks or ligation methods before the brackets are applied to a patient's teeth.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. IA illustrates an exemplary process to perform virtual treatment using one or more dental appliances.

[0010] FIG. 2 shows two different appliances, in this case brackets, in their own virtual spaces.

[0011] FIG. 3 shows the brackets of FIG. 2, isometrically displayed in the same virtual space.

[0012] FIG. 4 shows the substitution based on an alignment of the brackets' dimensions or features.

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DESCRIPTION

[0013] FIG. IA illustrates an exemplary process to perform virtual treatment using one or more dental appliances. The process includes receiving a digital model of a dental appliance (110); selecting a standard position and orientation (120); and mapping the digital model of the dental appliance to the standard position and orientation (130). [0014] In one embodiment, the appliance can be a bracket. The digital model of the bracket can be received from a scanner or digitizer. There are several means of digitizing the brackets, among them computer tomography, acoustic imaging, surface tracing, and destructive scanning. Any of these could be direct or indirect. The former digitizes the body itself. The latter digitizes an impression or a mold of the body. The data set produced by the 3D acquisition system may, of course, be converted to other formats to be compatible with the software which is used for manipulating 3D images within the data set. Additionally, a variety of range acquisition systems, generally categorized by whether the process of acquisition requires contact with the three dimensional object, can be used. A contact-type range acquisition system utilizes a probe, having multiple degrees of translational and/or rotational freedom. By recording the physical displacement of the probe as it is drawn across the sample surface, a computer-readable representation of the sample object is made. A non-contact-type range acquisition device can be either a reflective-type or transmissive-type system. There are a variety of reflective systems in use. Some of these reflective systems utilize non-optical incident energy sources such as microwave radar or sonar. Others utilize optical energy. Those non-contact-type systems working by reflected optical energy further contain special instrumentation configured to permit certain measuring techniques to be performed (e.g.,

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imaging radar, triangulation and interferometry). Optical, reflective, non-contact-type scanners and other non-contact-type scanners are preferred because they are inherently nondestructive (i.e., do not damage the sample object), are generally characterized by a higher capture resolution and scan a sample in a relatively short period of time. Next, a standard position and orientation is selected and the digital model of the dental appliance is mapped to the selected standard position and orientation.

[0015] A first embodiment to map appliances to the standard orientation and position is discussed next. When the physical brackets are digitized, they are held in the same position and orientation by a jig that allows them to be held in the same spatial location. In one embodiment, the bracket's slot can be used to attain the same location for models within a manufacturer's line as well as across manufacturers' lines because it is one of the most consistent geometric features with the greatest dimensional similarity among all brackets.

[0016] A second embodiment to map appliances to the standard orientations and positions is discussed below. This embodiment may be used independently of or in conjunction with the first embodiment discussed above. In this embodiment, the digital representations of the brackets are opened in software that can read the file format(s) — it is not required that the bracket representations are in the same format. For instance, one could be an STL and another can be an IGES5 STEP, or CAD native (e.g. Pro/E, SolidWorks, etc.) file. Next, two or more files are loaded into the same software space at one time. Alternatively, each representation is loaded into its own space and these, in turn, are loaded to a common space. One of the files is selected as the base bracket to determine orientations and positions, or a separate object or coordinate system is selected

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as the basis to determine bracket orientations and positions. Any other bracket in the software space is aligned on the base bracket or the basis using known or common dimensions and features. Examples of common dimensions and features: within some amount of tolerance, all manufacturers' bracket slots are either .018" (0.46mm) or .022" (0.56mm) in the occlusogingival direction, the slot lengths are typically specified so the midpoint is easily determined, and the 'slot point' and 'base point' can be identified from these two. Any other bracket is saved independently with its newly-defined position and orientation.

[0017] In the case of contralateral brackets, the steps above could be followed or a bracket can simply be mirrored relative to a reference plane or surface to create its contralateral.

[0018] If the manufacturers' digital representations are available, the process is essentially the same as discussed above, except there is no need to digitize physical models. The positioning and orienting is less complex because all referents will be defined in the digital representations.

[0019] FIG. IB shows an exemplary process for substituting dental appliances. First, an operator selects a model of a dental appliance previously placed on a tooth model (150). Next, the operator selects a model of a substitute dental appliance (160). The substitution can be based on a number of factors including fit, height of the appliance, comfort of the patient, or appearance of the appliance, among others. Based on the selection of the original model of the dental appliance and a substitute model of the appliance, the process of FIG. IB places the substitute model in place of the original model of the dental appliance based on the standard position and orientation (170)

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[0020] FIG. 2 shows two different brackets in their own virtual spaces. Their coordinate systems are different — not co-located as also can be seen by the difference in arrow orientations shown in the bottom left corner of each panel.

[0021] FIG. 3 shows the same two brackets isometrically displayed in the same virtual space. The coordinate system of the space does not coincide with that of either bracket. It can be seen that if one bracket were to replace the other, that the orientations, at least, would differ.

[0022] FIG. 4 shows that an alignment of the dimensions and/or features of the brackets causes them to have shared positions and orientations. If one is replaced with the other, these would not be changed in a virtual orthodontic setup.

[0023] The system can also be used to model the effects of more traditional appliances such as retainers, aligners and other removable dental appliances and therefore be used to generate optimal designs and treatment programs for particular patients. [0024] The model of the brackets can be displayed and manually positioned or manipulated using a suitable dental CAD system. In this embodiment, a bracket is positioned on a tooth based on a prescription. Should the user wish to use a different bracket, the user merely selects a different bracket and indicates to the computer that the new bracket is to be used. The system deletes the first bracket and inserts the new bracket in the same spatial position and orientation of the original bracket without requiring the user to manually place the new bracket at the same location of the original bracket.

[0025] Alternatively, the system can automatically place the brackets for the user. Li either a manual or automated placement system, the common coordinate system allows

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the user to select a substitute bracket and automatically insert the substitute bracket in place of the original bracket. A general flow of an exemplary process for defining and generating repositioning appliances for orthodontic treatment of a patient is discussed next. The process includes the methods, and is suitable for the apparatus, of the present invention, as will be described. The computational steps of the process are advantageously implemented as computer program modules for execution on one or more conventional digital computers.

[0026] As an initial step, a mold or a scan of a patient's teeth or mouth tissue is acquired. This generally involves taking casts of the patient's teeth and gums, and may also involve taking wax bites, direct contact scanning, x-ray imaging, tomographic imaging, sonographic imaging, and other techniques for obtaining information about the position and structure of the teeth, jaws, gums and other orthodontically relevant tissue. From the data so obtained, a digital data set is derived that represents the initial (that is, pretreatment) arrangement of the patient's teeth and other tissues. [0027] The initial digital data set, which may include both raw data from scanning operations and data representing surface models derived from the raw data, is processed to segment the teeth into individual tooth models for manipulation. Digital models of each tooth can be produced, including measured or extrapolated hidden surfaces and root structures.

[0028] The desired final position of the teeth - that is, the desired and intended end result of orthodontic treatment - can be received from a clinician in the form of a prescription, can be calculated from basic orthodontic principles, or can be extrapolated computationally from a clinical prescription. With a specification of the desired final

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positions of the teeth and digital representations of the teeth themselves, the final position and surface geometry of each tooth can be specified to form a complete model of the teeth at the desired treatment end. Generally, in this step, the position of every tooth is specified. The result of this step is a set of digital data structures that represents an orthodontically correct repositioning of the modeled teeth relative to presumed-stable tissue. The teeth and tissue are both represented as digital data. [0029] Having both a beginning position and a final position for each tooth, the process next defines a tooth path for the motion of each tooth. The tooth paths are optimized in the aggregate so that the teeth are moved in the quickest fashion with the least amount of round-tripping to bring the teeth from their initial positions to their desired final \ positions. (Round-tripping is any motion of a tooth in any direction other than directly toward the desired final position. Round-tripping is sometimes necessary to allow teeth to move past each other.) The tooth paths are segmented. The segments are calculated so that each tooth's motion within a segment stays within threshold limits of linear and rotational translation; In this way, the end points of each path segment can constitute a clinically viable repositioning, and the aggregate of segment end points constitute a clinically viable sequence of tooth positions, so that moving from one point to the next in the sequence does not result in a collision of teeth.

[0030] The threshold limits of linear and rotational translation are initialized, in one implementation, with default values based on the nature of the appliance to be used. More individually tailored limit values can be calculated using patient-specific data. The limit values can also be updated based on the result of an appliance-calculation, which may determine that at.one or more points along one or more tooth paths, the forces that can be

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generated by the appliance on the then-existing configuration of teeth and tissue is incapable of effecting the repositioning that is represented by one or more tooth path segments. With this information, the subprocess defining segmented paths can recalculate the paths or the affected subpaths.

[0031] At various stages of the process, and in particular after the segmented paths have been defined, the process can, and generally will, interact with a clinician responsible for the treatment of the patient. Clinician interaction can be implemented using a client process programmed to receive tooth positions and models, as well as path information from a server computer or process in which other processes are implemented. The client process is advantageously programmed to allow the clinician to display an animation of the positions and paths and to allow the clinician to reset the final positions of one or more of the teeth and to specify constraints to be applied to the segmented paths. If the clinician makes any such changes, the subprocess of defining segmented paths is performed again.

[0032] The data processing aspects of the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Data processing apparatus of the invention can be implemented in a computer program product tangibly embodied in a machine-readable storage device for execution by a programmable processor; and data processing method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions of the invention by operating on input data and generating output. The data processing aspects of the invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one

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programmable processor coupled to receive data and instructions from and to transmit data and instructions to a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language, if desired; and, in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, a processor will receive instructions and data from a read¬ only memory and/or a random access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of nonvolatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits). [0033] To provide for interaction with a user, the invention can be implemented using a computer system having a display device such as a monitor or LCD (liquid crystal display) screen for displaying information to the user and input devices by which the user can provide input to the computer system such as a keyboard, a two-dimensional pointing device such as a mouse or a trackball, or a three-dimensional pointing device such as a data glove or a gyroscopic mouse. The computer system can be programmed to provide a graphical user interface through which computer programs interact with users. The computer system can be programmed to provide a virtual reality, three-dimensional display interface.

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[0034] The invention has been described in terms of particular embodiments. Other embodiments are within the scope of the following claims. For example, the operations of the invention can be performed in a different order and still achieve desirable results.

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Claims

What is claimed is:

1. A method for performing virtual treatment using one or more dental appliances, comprising: receiving a digital model of a dental appliance; selecting a standard position and orientation; and mapping the digital model of the dental appliance to the standard position and orientation.

2. The method of claim 1 , wherein the mapping comprises setting a plurality of digital models to the standard spatial position and orientation.

3. The method of claim 1 , comprising placing a digital model of a first dental appliance on a tooth model.

4. The method of claim 3, comprising interchanging the first dental appliance with a second dental appliance.

5. The method of claim 4, comprising automatically placing the second dental appliance at the same position as the first dental appliance.

6. The method of claim 1, comprising scanning a dental appliance to create the digital model.

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7. The method of claim 1 , comprising selecting a base object to determine the standard orientation and position.

8. The method of claim 7, wherein the base object is one of the dental appliances.

9. The method of claim 7, wherein the base object is a separate object.

10. The method of claim 1 , comprising selecting a coordinate system as the basis for the standard orientation and position.

11. The method of claim 1 , wherein the standard position and orientation is determined using predetermined dimensions and features on the dental appliances.

12. The method of claim 11 , wherein one feature is an appliance slot.

13. The method of claim 12, wherein the slot comprises an .018" (0.46mm) or .022" (0.56mm) width channel running in a mesiodistal direction.

14. The method of claim 12, wherein one dimension comprises a slot length.

15. The method of claim 12, wherein one dimension comprises a slot point.

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16. The method of claim 12, wherein one dimension comprises a base point.

17. The method of claim 1, comprising associating the digital model of the dental appliance with reference to the standard position and orientation.

18. The method of claim 1 , wherein the dental appliance is a bracket.

19. The method of claim 18, wherein the bracket is a contralateral bracket, comprising mirroring the bracket relative to a reference plane or surface to create a contralateral model.

20. The method of claim 1, comprising interchanging the dental appliances in accordance with specified criteria.

21. The method of claim 20, wherein one criteria includes one of: a best fit on the tooth, a material fit, an obtrusiveness measure, and a cost.

22. The method of claim 1, comprising mapping an axis direction for the digital model.

23. The method of claim 1, comprising generating a template to place the dental appliance on a tooth.

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24. The method of claim 23, wherein the appliance is a bracket, comprising fabricating a wire based on the bracket's position and orientation.